The toxicity of hydrogen sulfide in hydrocarbons or hydrocarbon streams is well known in the industry and considerable expense and efforts are expended annually to reduce its content to a safe level. Many regulations require pipeline gas to contain no more than four (4) ppm hydrogen sulfide.
In large production facilities, it is generally more economical to install a regenerative system for treating streams containing hydrogen sulphide. These systems typically employ a compound used in an absorption tower to contact the produced fluids and selectively absorb the hydrogen sulfide and possibly other toxic materials such as carbon dioxide and mercaptans. The absorption compound is then regenerated and reused in the system. Typical hydrogen sulfide absorption materials include alkanolamines, hindered amines, and the like, i.e. nitrogen containing compounds. However, such approach is not economically feasible for development stage of a field or in small producing fields.
The nitrogen containing compounds, such as triazine, particularly monoethanolamine triazine (herein after the ‘monoethanolamine triazine’ may be referred to as ‘MEA Triazine’ or ‘MEAT’; and ‘triazine’ and ‘monoethanolamine triazine’ collectively may be referred to as ‘triazines’) are known as hydrogen sulfide scavengers (re PCT publication no. WO 90/07467; and US publication nos. US 2004/0096382 and US 2011/0220551).
However, use of triazines as hydrogen sulfide scavengers suffers from difficulties and problems. For example, triazines are not substantially effective for scavenging hydrogen sulfide in liquid hydrocarbon streams, and dry gas streams. Further, use of triazines may also result in scale formation particularly in sea water containing calcium ions and dissolved carbon dioxide. To overcome problem of scale formation, one has to flush an acid to remove the scales formed. Therefore, the industry aims to minimize the amount of nitrogen based hydrogen sulfide scavengers, i.e. triazines.